For generation of electric power both in tractional and in stationary applications, it is known to use gas turbines for driving electric generators. In applications with a varying power requirement, however, gas turbines exhibit certain disadvantages in that, at partial load, their efficiency is greatly deteriorated while at the same time the contents of environmentally harmful constituents in the exhaust gases are increased. It is also known that these disadvantages can be avoided by means of a control adapted to maintain the inlet temperature of the gas turbine at an even and high value. Thus, a system has been suggested where the guide vanes of the compressor in dependence on the load requirement are oriented such that the inlet temperature of the turbine is maintained substantially constant [Bulletin of the Royal Academy of Belgium; 5th Seiries, Volume XLI, 1955, A. Jaumotte: Control of Constant Speed and Constant Maximum Temperature of a Gas Turbine with Open Circuit on One Shaft]. The suggested solution means a mechanically complicated design owing to the fact that the generator driven by the gas turbine is connected to a stiff alternating-voltage network and the speed of the gas turbine thus bound to the frequency thereof. Therefore, particularly in applications where the speed of the gas turbine can be allowed to vary, a mechanically simpler solution is desirable.